Right-to-left shunt

Right-to-left shunt

A right-to-left shunt is a cardiac shunt which allows, or is designed to cause, blood to flow from the right heart to the left heart. [DorlandsDict|seven/000096626|right-to-left shunt] This terminology is used both for the abnormal state in humans and for normal physiological shunts in reptiles.

Human medical

A right-to-left shunt occurs when:
#there is an opening or passage between the atria, ventricles, and/or great vessels; "and",
#right heart pressure is higher than left heart pressure and/or the shunt has a one-way valvular opening.

The most common cause of right-to-left shunt is the Tetralogy of Fallot, a congenital cardiac anomaly characterized by four co-existing heart defects. The four defects include:

#Pulmonary stenosis (narrowing of the pulmonary valve and outflow tract, obstructing blood flow from the right ventricle to the pulmonary artery)
#Ventricular septal defect (defect in the ventricular septum, which divides the left and right ventricles of the heart)
#Overriding aorta (aortic valve is enlarged and appears to arise from both the left and right ventricles instead of the left ventricle, as occurs in normal hearts)
#Right ventricular hypertrophy (thickening of the muscular walls of the right ventricle)

A right to left shunt frequently causes hypoxemia.

Reptiles

Because most reptiles have a single ventricle and all reptiles have both a right aortic arch and a left aortic arch, all reptiles have the capacity for right-to-left shunt. Fact|date=August 2008

References


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